Vegetation Reconstruction From Siberia and the Tibetan Plateau Using Modern Analogue Technique–Comparing Sedimentary (Ancient) DNA and Pollen Data

Sisi Liu,Kathleen Rosmarie Stoof-Leichsenring,Weihan Jia,Kai Li,Xianyong Cao,Xingqi Liu,Ulrike Herzschuh

doi:10.3389/fevo.2021.668611

Abstract

To reconstruct past vegetation from pollen or, more recently, lake sedimentary DNA (sedDNA) data is a common goal in palaeoecology. To overcome the bias of a researcher’s subjective assessment and to assign past assemblages to modern vegetation types quantitatively, the modern analogue technique (MAT) is often used for vegetation reconstruction. However, a rigorous comparison of MAT-derived pollen-based and sedDNA-based vegetation reconstruction is lacking. Here, we assess the dissimilarity between modern taxa assemblages from lake surface-sediments and fossil taxa assemblages from four lake sediment cores from the south-eastern Tibetan Plateau and northern Siberia using receiver operating characteristic (ROC) curves, ordination methods, and Procrustes analyses. Modern sedDNA samples from 190 lakes and pollen samples from 136 lakes were collected from a variety of vegetation types. Our results show that more modern analogues are found with sedDNA than pollen when applying similarly derived thresholds. In particular, there are few modern pollen analogues for open vegetation such as alpine or arctic tundra, limiting the ability of treeline shifts to be clearly reconstructed. In contrast, the shifts in the main vegetation communities are well captured by sedimentary ancient DNA (sedaDNA). For example, pronounced shifts from late-glacial alpine meadow/steppe to early–mid-Holocene coniferous forests to late Holocene Tibetan shrubland vegetation types are reconstructed for Lake Naleng on the south-eastern Tibetan Plateau. Procrustes and PROTEST analyses reveal that intertaxa relationships inferred from modern sedaDNA datasets align with past relationships generally, while intertaxa relationships derived from modern pollen spectra are mostly significantly different from fossil pollen relationships. Overall, we conclude that a quantitative sedaDNA-based vegetation reconstruction using MAT is more reliable than a pollen-based reconstruction, probably because of the more straightforward taphonomy that can relate sedDNA assemblages to the vegetation surrounding the lake.

Highlights

Clarke et al, 2019)
For the modern pollen training-set, we find the vegetation types of Siberia are placed on the left side of the principal component analysis (PCA) plot, separated from the vegetation types of China which are located on the right side (Figure 6B)
In this study we compared surface sedimentary DNA (sedDNA)/pollen assemblages from China and northern Siberia with sedimentary ancient DNA (sedaDNA)/fossil pollen assemblages from a record in Hengduan Mountains and three records from the treeline area in north-eastern Siberia (Omology region)

Summary

Introduction

Clarke et al, 2019). the commonly used plant sed(a)DNA metabarcoding using the g-h primer (Taberlet et al., 2007) has a higher taxonomic resolution than pollen for most taxa: typically to genus or species level (Bálint et al, 2018).Recently, several studies have been published that show the potential of sedaDNA plant metabarcoding for late Quaternary vegetation reconstruction in North Greenland (Epp et al, 2015), Svalbard (Alsos et al, 2016; Zimmermann et al, 2020), northernFennoscandia (Rijal et al, 2020), Russian Far East (Huang et al., 2020), Arctic Canada (Crump et al, 2019), and northern Siberia (Liu et al, 2020).A few statistical techniques are routinely adopted for analysing sedaDNA data with respect to quantifying species diversity and testing the environment-community relationship (reviewed by Chen and Ficetola, 2020). The commonly used plant sed(a)DNA metabarcoding using the g-h primer (Taberlet et al., 2007) has a higher taxonomic resolution than pollen for most taxa: typically to genus or species level (Bálint et al, 2018). The applicability of the modern analogue technique (MAT) and other methods comparing modern sedDNA and sedaDNA have not been investigated. We investigate whether MAT applied to plant DNA metabarcoding data can help to infer long-term changes in vegetation type. We compare modern taxa assemblages derived from sedDNA analyses of 190 lake surface-sediment samples and 136 pollen samples from lake surface-sediments from China and Siberia to fossil assemblages from four lake sediment cores

Methods

Discussion

Conclusion